394781891 has 4 divisors (see below), whose sum is σ = 451179312. Its totient is φ = 338384472.

The previous prime is 394781879. The next prime is 394781909. The reversal of 394781891 is 198187493.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198187493 = 7 ⋅28312499.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-394781891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (394781801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28198700 + ... + 28198713.

It is an arithmetic number, because the mean of its divisors is an integer number (112794828).

Almost surely, 2^394781891 is an apocalyptic number.

394781891 is a deficient number, since it is larger than the sum of its proper divisors (56397421).

394781891 is an equidigital number, since it uses as much as digits as its factorization.

394781891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56397420.

The product of its digits is 435456, while the sum is 50.

The square root of 394781891 is about 19869.1190292876. The cubic root of 394781891 is about 733.5883194327.

The spelling of 394781891 in words is "three hundred ninety-four million, seven hundred eighty-one thousand, eight hundred ninety-one".